1. Technical Field
The present disclosure relates to a hybrid vehicle.
2. Description of Related Art
Conventionally, there is suggested a hybrid vehicle (see, for example, Japanese Patent Application Publication No. 2003-201880 (JP 2003-201880 A)). This hybrid vehicle includes a generator-motor connected to a sun gear of a planetary gear, an engine connected to a carrier, a drive shaft connected to a ring gear, a propelling motor connected to the drive shaft, and a one-way clutch that prohibits reverse rotation (negative rotation) of the engine. In this hybrid vehicle, during a stop of the engine, when maximum acceleration is being required and when an estimated total torque of the propelling motor and the generator-motor is smaller than a maximum total torque of the propelling motor and the engine, the engine is started.
The hybrid vehicle having the above-described hardware configuration is able to select a so-called double-drive mode in which the hybrid vehicle travels by using torque from the propelling motor and torque from the generator-motor (torque in a direction to rotate the generator-motor in the negative direction) while the engine is placed in a rotation stopped state. At the time of starting the engine, the engine is cranked by using torque from the generator-motor (torque in a direction to rotate the generator-motor in the positive direction). Thus, the engine is started. Therefore, at the time of starting the engine in the double-drive mode, the direction of torque from the generator-motor reverses, so the direction of torque that is output from the generator-motor to act on the drive shaft reverses, with the result that there is a possibility that the total torque that is output to the drive shaft reduces by a large amount to some extent. At the time of starting the engine because of the fact that a required torque becomes larger than a start threshold, it is presumable that a driver is increasing an accelerator operation amount (issuing an acceleration request). For this reason, if the above-described phenomenon occurs, the driver may experience a feeling of slowness. For this reason, when it is assumed that the required torque becomes relatively large after the present time, it is desirable to take measures in advance in order not to cause the driver to experience a feeling of slowness at the time of starting the engine.